Flight Incheon International Airport departs from Seoul Incheon International Airport at 19:05 and arrives at Singapore Changi Airport at 00:35.
The flighttime is about 6h 30m. The distance travelled ("as the bird flies"): 2923 Km. So the average speed is roughly 450 Km.
There is an 1 hour time difference between Seoul and Singapore
The best day to arrive at Seoul is Thursday and it would be best to avoid Monday, as prices are on average 144.46% higher than on Thursday. (Average prices, based on 688940 datapoints.)
We have a lot more statistics for flights OZ 753 and between Seoul and Singapore.